Llyn Padarn is a glacially formed lake in Snowdonia, Gwynedd, north Wales, and is an example of a moraine dammed lake. The lake is approximately 2 miles (3.2 km) long (about 240 acres) and at its deepest point is 94 feet (29 m) deep, and is one of the largest natural lakes in Wales. At its south-eastern end it is linked to the neighbouring Llyn Peris (which forms the lower reservoir of the Dinorwig power station). The busy village of Llanberis lies on the southern banks of the lake.
The majority of Llyn Padarn is owned by Gwynedd Council and is part of Padarn Country Park. Whilst kayaking, rowing and sailing are permitted on the lake, power boats are NOT permitted without consent from the owners. The Bangor University Rowing Club row at Llyn Padarn.
In April 2014 Llyn Padarn was designated as Bathing Water under the Bathing Water Directive (2006/7/EC).